Baltimore Ecosystem Study Institute of Ecosystem Studies

2016 BES Annual Meeting Presentation and Poster Abstracts

Patterns of turbidity, sediment concentration, and load in a nested urban watershed
Kemper, John T
Co-Authors: John Kemper, Andrew Miller and Claire Welty

Abstract: While suspended sediment is a matter of primary concern in highly regulated watersheds, few continuous sediment-concentration records exist to quantify urban sediment loads. Near real-time turbidity and discharge data have been collected continuously for more than three years at five stream gages representing three nested watershed scales (1-2 sq km, 5-6 sq km, 14 sq km) in the highly impervious Dead Run watershed. Suspended sediment point samples have been collected for multiple storm events at each site to establish provisional relationships between turbidity and suspended sediment concentrations. Sediment concentration-stream discharge relationships were examined for storms of varying magnitude for 2014-2016. Relationships varied both spatially and temporally, highlighting the extreme heterogeneity of an urban watershed. Spatially, C-Q relationships changed from headwaters to mouth, potentially suggesting a variation in sediment sources. Temporally, C-Q relationships differed on both a storm and seasonal scale, implying inconsistent patterns of sediment arrival and again suggesting a variation in sediment sources. Sediment loads did not consistently scale with watershed area. Yields at one headwater station (DR5) were consistent with yields at the downstream site (DR4), while yields at the other (DR2) were consistently lower than yields at the downstream site (DR3). Furthermore, yields at the furthest downstream site (DRKR) for large storms were higher than a weighted average of the two contributing sites, potentially suggesting additional source areas of sediment within the watershed. This highlights the ability of near real-time data to assist in identifying consistent trends, locations of hot spots, and patterns of sediment arrival.